Source

function wp_kses_check_attr_val( $value, $vless, $checkname, $checkvalue ) {
$ok = true;
switch ( strtolower( $checkname ) ) {
case 'maxlen':
/*
* The maxlen check makes sure that the attribute value has a length not
* greater than the given value. This can be used to avoid Buffer Overflows
* in WWW clients and various Internet servers.
*/
if ( strlen( $value ) > $checkvalue ) {
$ok = false;
}
break;
case 'minlen':
/*
* The minlen check makes sure that the attribute value has a length not
* smaller than the given value.
*/
if ( strlen( $value ) < $checkvalue ) {
$ok = false;
}
break;
case 'maxval':
/*
* The maxval check does two things: it checks that the attribute value is
* an integer from 0 and up, without an excessive amount of zeroes or
* whitespace (to avoid Buffer Overflows). It also checks that the attribute
* value is not greater than the given value.
* This check can be used to avoid Denial of Service attacks.
*/
if ( ! preg_match( '/^\s{0,6}[0-9]{1,6}\s{0,6}$/', $value ) ) {
$ok = false;
}
if ( $value > $checkvalue ) {
$ok = false;
}
break;
case 'minval':
/*
* The minval check makes sure that the attribute value is a positive integer,
* and that it is not smaller than the given value.
*/
if ( ! preg_match( '/^\s{0,6}[0-9]{1,6}\s{0,6}$/', $value ) ) {
$ok = false;
}
if ( $value < $checkvalue ) {
$ok = false;
}
break;
case 'valueless':
/*
* The valueless check makes sure if the attribute has a value
* (like `<a href="blah">`) or not (`<option selected>`). If the given value
* is a "y" or a "Y", the attribute must not have a value.
* If the given value is an "n" or an "N", the attribute must have a value.
*/
if ( strtolower( $checkvalue ) != $vless ) {
$ok = false;
}
break;
} // End switch.
return $ok;
}